Osteoporosis is often referred to as the “silent disease” because bone loss occurs without symptoms. It affects 55% of Americans over the age of 50, and incurs a medical cost of $47 million a day. Osteoporosis is caused by a disruption in the fine equilibrium between bone resorption and bone deposition. Where osteoblasts control bone deposition and osteoclasts control its resorption. Our poor understanding on the molecular control of bone deposition has lead to many pharmaceutical drugs targeting bone resorption only, i.e. Oestrogen Therapy & Bisphosphonates. Bone deposition was thought to be regulated mainly by the Bone Morphogenetic Protein (BMP) pathway. However, recent data has lead to the discovery of another “bone deposition thermostat,” called LRP5. This discovery began with positional cloning of the dominant High Bone Mass (HBM) trait found in Humans. In addition, a loss of LRP5 results in Osteoporosis Pseudoglioma (OPPG) Syndrome that is characterized by a decrease in bone mass. LRP5 is therefore an important player in the regulation of bone deposition. LRP5 has been shown to function as a membrane co-receptor for the WNT pathway. Only since the discovery of LRP5 has the WNT pathway been known to play a pivotal role in bone mass regulation.